Mode control for mechanical transmission system with semi-automatic shift implementation and manual and automatic shift preselection modes

ABSTRACT

A mode control method/system for a control system (104) for semi-automatically executing automatically and manually selected upshifts and downshifts of a mechanical transmission system (10) is provided. The control system includes a central processing unit (106) for receiving input signals indicative of transmission input shaft (16) and output shaft (90) speeds and from a driver control console (108) indicative of manual selection of upshifts or downshifts from a currently engaged gear ratio, or manual selection of operation in an automatic preselect mode, and processing the same in accordance with predetermined logic rule to issue command output signals to a transmission actuator (112, 70, 96) to implement the selected shifts by automatic shifting into neutral upon a naturally or manually caused torque reversal of the transmission and remaining in neutral until the vehicle operator causes substantially synchronous conditions to occur. The method (200) includes sensing if output shaft speed remains substantially constant and the transmission is not shifted (Shift=F) for a predetermined time (REF) and then causing the system to operate in the manually selected shift mode of operation.

RELATED APPLICATIONS

This Application is related to U.S. applications Ser. No. 368,467,titled AUTOMATIC SHIFT PRESELECTION MODE FOR MECHANICAL TRANSMISSIONSYSTEM WITH SEMI-AUTOMATIC SHIFT IMPLEMENTATION; Ser. No. 368,011,titled SEMI-AUTOMATIC SHIFT IMPLEMENTATION FOR MECHANICAL TRANSMISSIONSYSTEM; Ser. No. 368,502, titled CONTROL SYSTEM AND METHOD FOR SENSINGAND INDICATING NEUTRAL IN A SEMI-AUTOMATIC MECHANICAL TRANSMISSIONSYSTEM; Ser. No. 368,492, titled ENHANCED MISSED SHIFT RECOVERY FORSEMI-AUTOMATIC SHIFT IMPLEMENTATION CONTROL SYSTEM; and Ser. No.368,500, titled CONTROL SYSTEM/METHOD FOR CONTROLLING SHIFTING OF ARANGE TYPE COMPOUND TRANSMISSION USING INPUT SHAFT AND MAINSHAFT SPEEDSENSORS; all assigned to Eaton Corporation, the assignee of thisApplication, and all filed June 19, 1989.

This application is also related to U.S. Application Ser. No. 568,798,entitled UNEXPECTED N LOGIC, assigned to Eaton Corporation, the assigneeof this application and filed the same day as this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to vehicular semi-automatic mechanicaltransmission systems and, in particular, to semi-automatic mechanicaltransmission systems of the type providing partially automaticimplementation, including an automatic shift into neutral, ofpreselected shifts and having a manual preselect mode and at least oneautomatic preselect mode of operation wherein ratio changes areautomatically preselected by the system central processing unit.

More particularly, the present invention relates to semi-automatictransmission of the type described above wherein, in the operatorselected automatic preselection mode of operation, if vehicle speed(output shaft speed) remains substantially constant and a shift is notselected/completed for a preselected period of time, then automaticpreselection of shifts and shifts into neutral are discontinued until ashift is manually selected by the operator to preventunexpected/undesired transmission shifts into transmission neutral.

2. Description of the Prior Art

Fully automatic transmission systems, both for heavy-duty vehicles suchas heavy-duty trucks, and for automobiles, that sense throttle openingsor positions, vehicle speeds, engine speeds, and the like, andautomatically shift the vehicle transmission in accordance therewith,are well known in the prior art. Such fully automatic change geartransmission systems include automated transmissions wherein pressurizedfluid is utilized to frictionally engage one or more members to othermembers or to a ground to achieve a selected gear ratio as well asautomated mechanical transmissions utilizing electronic, hydraulic,and/or pneumatic logic and actuators to engage and disengage mechanical(i.e. positive) clutches to achieve a desired gear ratio. Examples ofsuch transmissions may be seen by reference to U.S. Pat. Nos. 3,961,546;4,081,065; 4,361,060 and 4,551,802; the disclosures of which are herebyincorporated by reference.

Such fully automatic change gear transmissions can be unacceptablyexpensive, particularly for the largest heavy-duty vehicles which arenot typically sold in high volumes. Additionally, those automatic changegear transmissions utilizing pressurized fluid and/or torque converterstend to be relatively inefficient in terms of power dissipated betweenthe input and output shafts thereof.

Semi-automatic transmission systems utilizing electronic control unitswhich sense throttle position, engine, input shaft, output shaft and/orvehicle speed, and utilize automatically controlled fuel throttledevices, gear shifting devices and/or master clutch operating devices tosubstantially fully automatically implement operator manually selectedtransmission ratio changes are known in the prior. Examples of suchsemi-automatic transmission systems may be seen by reference to U.S.Pat. Nos. 4,425,620; 4,631,679 and 4,648,290, the disclosures of whichare incorporated herein by reference.

While such semi-automatic mechanical transmission systems are very wellreceived as they are somewhat less expensive than fully automatictransmission systems, allow manual clutch control for low speedoperation and/or do not require automatic selection of the operatinggear ratio, they may be too expensive for certain applications as arelatively large number of sensors and automatically controllableactuators, such as a master clutch and/or a fuel throttle deviceactuator, are required to be provided, installed and maintained.

Many of the drawbacks of the prior art are overcome or minimized by theprevious provision of a semi-automatic shift implementationsystem/method for a mechanical transmission system for use in vehicleshaving a manually or partially automatically controlled engine throttlemeans, and a manually only controlled master clutch. The system has amanual preselection mode wherein shifts are manually preselected and atleast one mode of operation wherein the shifts to be semi-automaticallyimplemented are automatically preselected and includes a control/displaypanel or console for operator selection of operation in the automaticpreselection mode and indication of automatic preselection of upshifts,downshifts or shifts into neutral. An electronic control unit (ECU) isprovided for receiving input signals indicative of transmission inputand output shaft speeds and for processing same in accordance withpredetermined logic rules to determine, in the automatic preselectionmode, if an upshift or downshift from the currently engaged ratio isrequired and to issue command output signals to a transmission actuatorfor shifting the transmission in accordance with the command outputsignals.

The control/display device will display the selected but not yetimplemented shift as well as the current status of the transmission,and, preferably will allow the operator to select/preselect a shift intoa higher ratio, a lower ratio or into neutral. Preferably, the controldevice will also allow a manually or an automatically preselected shiftto be cancelled.

In both the manual and the automatic preselection modes, when a ratiochange is manually or automatically preselected, the transmission willautomatically be caused to shift to neutral and will then shift to theselected ratio only upon the operator manually causing a substantiallysynchronous condition to exist.

In accordance with the previously proposed control, a controlsystem/method for a vehicular semi-automatic mechanical transmissionsystem for partially automatic implementation of manually andautomatically preselected transmission shifts was provided which did notrequire throttle or clutch actuators, and which required only two speedsignal inputs. However, this system was not totally satisfactory as,after a long period of relatively stable vehicle operating conditions,i.e. vehicle speed substantially constant and no gear shiftingoccurring, the automatic shifting of the transmission into, andremaining in, neutral may be undesired, unexpected and/or startling tothe operator.

SUMMARY OF THE INVENTION

In accordance with the present invention, a control system/method whichminimizes or eliminates the drawback of unexpected/undesired shiftinginto and remaining in neutral of the previously proposed controlsystem/method for a vehicular semi-automatic mechanical transmissionsystem for partially automatic implementation of manually andautomatically selected transmission shifts, which does not require anautomatic clutch actuator, and which requires only two speed signalinputs, is provided.

The above is accomplished, in the previously proposed controlsystem/method, by monitoring vehicle (output shaft) speed andtransmission shifting and, if, for a predetermined period of time (60seconds for example), the vehicle speed remains substantially constantand the transmission is not shifted, then the control will revert tooperation in the manual preselection mode, regardless of mode selectedby the vehicle operator, wherein the vehicle operator must manuallypreselect desired gear ratio changes.

This and other objects and advantages of the present invention willbecome apparent from a reading of the detailed description of thepreferred embodiment taken in connection with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of the vehicular mechanicaltransmission system partially automated by the system of the presentinvention.

FIG. 1A is a schematic illustration of the shift pattern of thetransmission of FIG. 1.

FIG. 2 is a schematic illustration of the automatic preselect andsemi-automatic shift implementation system for a mechanical transmissionsystem of the present invention.

FIG. 3 is a schematic illustration of an alternate control console forthe system of FIG. 2.

FIG. 4 is a schematic illustration, in the form of a flow chart, of theenhanced control system/method of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Certain terminology will be used in the following description forconvenience in reference only and will not be limiting. The words"upwardly", "downwardly", "rightwardly", and "leftwardly" will designatedirections in the drawings to which reference is made. The words"forward", "rearward", will refer respectively to the front and rearends of the transmission as conventionally mounted in a vehicle, beingrespectfully from left and right sides of the transmission asillustrated in FIG. 1. The words "inwardly" and "outwardly" will referto directions toward and away from, respectively, the geometric centerof the device and designated parts thereof. Said terminology willinclude the words above specifically mentioned, derivatives thereof andwords of similar import.

The term "compound transmission" is used to designate a change speed orchange gear transmission having a multiple forward speed maintransmission section and a multiple speed auxiliary transmission sectionconnected in series whereby the selected gear reduction in the maintransmission section may be compounded by further selected gearreduction in the auxiliary transmission section. "Synchronized clutchassembly" and words of similar import shall designate a clutch assemblyutilized to nonrotatably couple a selected gear to a shaft by means of apositive clutch in which attempted engagement of said clutch isprevented until the members of the clutch are at substantiallysynchronous rotation in a relatively large capacity friction means areutilized with the clutch members and are sufficient, upon initiation ofa clutch engagement, to cause the clutch members and all membersrotating therewith to rotate at substantially synchronous speed.

The term "upshift" as used herein, shall mean the shifting from a lowerspeed gear ratio into a higher speed gear ratio. The term "downshift" asused herein, shall mean the shifting from a higher speed gear ratio to alower speed gear ratio. The terms "low speed gear", "low gear" and/or"first gear" as used herein, shall all designate the gear ratio utilizedfor lowest forward speed operation in a transmission or transmissionsection, i.e., that set of gears having the highest ratio of reductionrelative to the input shaft of the transmission.

A "selected direction" of shifting will refer to selection of eithersingle or multiple upshifting or downshifting from a particular gearratio.

Referring to FIG. 1, a range type compound transmission 10 of the typepartially automated by the enhanced semi-automatic mechanicaltransmission system/method of the present invention is illustrated.Compound transmission 10 comprises a multiple speed main transmissionsection 12 connected in series with a range type auxiliary section 14.Transmission 10 is housed within a housing H and includes an input shaft16 driven by a prime mover such as diesel engine E through a selectivelydisengaged, normally engaged friction master clutch C having an input ordriving portion 18 drivingly connected to the engine crankshaft 20 and adriven portion 22 rotatably fixed to the transmission input shaft 16.

The engine E is fuel throttle controlled by a manually controlledthrottle device (not shown) and the master clutch C is manuallycontrolled by a clutch pedal (not shown) or the like. An input shaftbrake B, operated by overtravel depression of the clutch pedal, ispreferably provided to provide quicker upshifting as is well known inthe prior art.

Transmissions similar to mechanical transmission 10 are well known inthe prior art and may be appreciated by reference to U.S. Pat. Nos.3,105,395; 3,283,613 and 4,754,665, the disclosures of which areincorporated by reference.

In main transmission section 12, the input shaft 16 carries an inputgear 24 for simultaneously driving a plurality of substantiallyidentical countershaft assemblies 26 and 26A at substantially identicalrotational speeds. The two substantially identical countershaftassemblies are provided on diametrically opposite sides of mainshaft 28which is generally coaxially aligned with the input shaft 16. Each ofthe countershaft assemblies comprises a countershaft 30 supported bybearings 32 and 34 in housing H, only a portion of which isschematically illustrated. Each of the countershafts is provided with anidentical grouping of countershaft gears 38, 40, 42, 44, 46 and 48,fixed for rotation therewith. A plurality of mainshaft gears 50, 52, 54,56 and 58 surround the mainshaft 28 and are selectively clutchable, oneat a time, to the mainshaft 28 for rotation therewith by sliding clutchcollars 60, 62 and 64 as is well known in the prior art. Clutch collar60 may also be utilized to clutch input gear 24 to mainshaft 28 toprovide a direct drive relationship between input shaft 16 and mainshaft28.

Typically, clutch collars 60, 62 and 64 are axially positioned by meansof shift forks associated with the shift housing assembly 70, as wellknown in the prior art. Clutch collars 60, 62 and 64 may be of the wellknown acting nonsynchronized double acting jaw clutch type.

Shift housing or actuator 70 is actuated by compressed fluid, such ascompressed air, and is of the type automatically controllable by acontrol unit as may be seen by reference to U.S. Pat. Nos. 4,445,393;4,555,959; 4,361,060; 4,722,237 and 2,931,237, the disclosures of whichare incorporated by reference.

Mainshaft gear 58 is the reverse gear and is in continuous meshingengagement with countershaft gears 48 by means of conventionalintermediate idler gears (not shown). It should also be noted that whilemain transmission section 12 does provide five selectable forward speedratios, the lowest forward speed ratio, namely that provided bydrivingly connecting mainshaft drive gear 56 to mainshaft 28, is oftenof such a high gear reduction it has to be considered a low or "creeper"gear which is utilized only for starting of a vehicle under severeconditions and, is not usually utilized in the high transmission range.Accordingly, while main transmission section 12 does provide fiveforward speeds, it is usually referred to as a "four plus one" mainsection as only four of the forward speeds are compounded by theauxiliary range transmission section 14 utilized therewith.

Jaw clutches 60, 62, and 64 are three-position clutches in that they maybe positioned in the centered, nonengaged position as illustrated, or ina fully rightwardly engaged or fully leftwardly engaged position bymeans of actuator 70. As is well known, only one of the clutches 60, 62and 64 is engageable at a given time and main section interlock means(not shown) are provided to lock the other clutches in the neutralcondition.

Auxiliary transmission range section 14 includes two substantiallyidentical auxiliary countershaft assemblies 74 and 74A, each comprisingan auxiliary countershaft 76 supported by bearings 78 and 80 in housingH and carrying two auxiliary section countershaft gears 82 and 84 forrotation therewith. Auxiliary countershaft gears 82 are constantlymeshed with and support range/output gear 86 while auxiliary sectioncountershaft gears 84 are constantly meshed with output gear 88 which isfixed to transmission output shaft 90.

A two-position synchronized jaw clutch assembly 92, which is axiallypositioned by means of a shift fork not shown) and the range sectionshifting actuator assembly 96, is provided for clutching either gear 86to mainshaft 28 for low range operation or gear 88 to mainshaft 28 fordirect or high range operation of the compound transmission 10. The"shift pattern" for compound range type transmission 10 is schematicallyillustrated in FIG. 1A.

Range section actuator 96 may be of the type illustrated in U.S. Pat.Nos. 3,648,546; 4,440,037 and 4,614,126, the disclosures of which arehereby incorporated by reference.

Although the range type auxiliary section 14 is illustrated as atwo-speed section utilizing spur or helical type gearing, it isunderstood that the present invention is also applicable to range typetransmissions utilizing combined splitter/range type auxiliary sections,having three or more selectable range ratios and/or utilizing planetarytype gearing. Also, any one or more of clutches 60, 62 or 64 may be ofthe synchronized jaw clutch type and transmission sections 12 and/or 14may be of the single countershift type.

For purposes of providing the manual preselect mode of operation and theautomatic preselect mode of operation, and the semi-automatic shiftimplementation operation of transmission 10, an input shaft speed sensorand an output shaft speed sensor 100 are utilized. Alternatively tooutput shaft speed sensor 100, a sensor 102 for sensing the rotationalspeed of auxiliary section countershaft gear 82 may be utilized. Therotational speed of gear 82 is, of course, a known function of therotational speed of mainshaft 28 and, if clutch 92 is engaged in a knownposition, a function of the rotational speed of output shaft 90.

The manual and automatic preselect and semi-automatic shiftimplementation control system 104 for a mechanical transmission systemof the present invention is schematically illustrated in FIG. 2. Controlsystem 104, in addition to the mechanical transmission system 10described above, includes an electronic control unit 106, preferablymicroprocessor based, for receiving input signals from the input shaftspeed sensor 98, from the output shaft speed sensor 100 (or,alternatively, the mainshaft speed sensor 102) and from the drivercontrol console 108. The ECU 106 may also receive inputs from anauxiliary section position sensor 110.

The ECU is effective to process the inputs in accordance withpredetermined logic rules to issue command output signals to atransmission operator, such as solenoid manifold 112 which controls themainsection section actuator 70 and the auxiliary section actuator 96,and to the driver control console 108. ECUs of this type are known inthe Prior art as may be seen by reference to U.S. Pat. No. 4,595,986,the disclosure of which is incorporated by reference.

In the preferred embodiment, the driver control counsel allows theoperator to manually select a shift in a given direction or to neutralfrom the currently engaged ratio, or to select a semi-automaticpreselect mode of operation, and provides a display for informing theoperator of the current mode of operation (automatic or manualpreselection of shifting), the current transmission operation condition(forward, reverse or neutral) and of any ratio change or shift (upshift,downshift or shift to neutral) which has been preselected but not yetimplemented.

Console 108 includes three indicator lights 114, 116 and 118 which willbe lit to indicate that the transmission 10 is in a forward drive,neutral or reverse drive, respectively, condition. The console alsoincludes three selectively lighted pushbuttons 120, 122, and 124 whichallow the operator to select an upshift, automatic preselection mode ora downshift, respectively. A pushbutton 126 allows selection of a shiftinto neutral.

A selection made by depressing or pushing any one of buttons 120, 122,124 or 126 and may be cancelled (prior to execution in the case ofbuttons 120, 124 and 126) by redepressing the buttons. As analternative, multiple depressions of buttons 120 and 124 may be used ascommands for skip shifts. Of course, the buttons and lighted buttons canbe replaced by other selection means, such as a toggle switch and/or atoggle switch and light or other indicia member. A separate button orswitch for selection of reverse may be provided or reverse may beselected as a downshift from neutral. Also, neutral may be selected asan upshift from reverse or as a downshift from low.

In operation, to select upshifts and downshifts manually, the operatorwill depress either button 120 or button 124 as appropriate. Theselected button will then be lighted until the selected shift isimplemented or until the selection is cancelled.

Alternatively, at a given engine speed (such as above 1700 RPM) theupshift button may be lit and remain lit until an upshift is selected bypushing the button.

To implement a selected shift, the manifold 112 is preselected to causeactuator 70 to be biased to shift main transmission section 12 intoneutral. This is usually accomplished by a naturally occurring torquereversal in the vehicle drive train or the operator causing a torquereversal by manually momentarily decreasing and/or increasing the supplyof fuel to the engine and/or manually disengaging the master clutch C.As the transmission is shifted into neutral, and neutral is verified bythe ECU (neutral sensed for a period of time such as 1.5 seconds), theneutral condition indicia button 116 is lighted. If the selected shiftis a compound shift, i.e. a shift of both the main section 12 and of therange section 14, such as a shift from 4th to 5th speeds as seen in FIG.1A, the ECU will issue command output signals to manifold 112 to causethe auxiliary section actuator 96 to complete the range shift afterneutral is sensed in the front box.

When the range auxiliary section is engaged in the proper ratio, the ECUwill calculate or otherwise determine, and continue to update, anenabling range or band of input shaft speeds, based upon sensed outputshaft (vehicle) speed and the ratio to be engaged, which will result inan acceptably synchronous engagement of the ratio to be engaged. As theoperator, by throttle manipulation and/or use of the input shaft brake,causes the input shaft speed to fall within the acceptable range, theECU 106 will issue command output signals to manifold 112 to causeactuator 70 to engage the mainsection ratio to be engaged. Preferably,the actuator will respond very quickly not requiring the operator tomaintain the input shaft speed within the acceptable range for anextended period of time. To select a shift into transmission neutral,selection button 126 is pushed. Indicating light 116 will flash untilthe ECU confirms that neutral is obtained at which time the light 116will assume a continuously lighted condition while the transmissionremains in neutral.

In the automatic preselection mode of operation, selected by use oflighted pushbutton 122, the ECU will, based upon stored logic rules,currently engaged ratio (which may be calculated by comparing inputshaft to output shaft speed) and output shaft or vehicle speed,determine if an upshift or a downshift is required and preselect same.The operator is informed that an upshift or downshift is preselected andwill be semi-automatically implemented by a command output signal fromECU 106 causing either lighted pushbutton 120 or lighted pushbutton 124to flash and/or an audible shift alert signal. The operator may initiatesemi-automatic implementation of the automatically preselected shift asindicated above or may cancel the automatic mode and the shiftpreselected thereby by depression of pushbutton 122.

As an alternative, the neutral condition indication light 116 may beeliminated and neutral selection pushbutton 126 replaced by a lightedpushbutton.

An alternate driver control and display console 130 may be seen byreference to FIG. 3. A joy stick 132 is movable against a resilient biasfrom its centered position to select upshifts, downshifts, a shift toneutral or the automatic preselect mode by movement up, down, leftwardor rightward, respectively, as indicated. Indicia lights 134 and 136 arelighted to indicate an upshift or downshift, respectively, ispreselected. Indicia lights 138 and 140, respectively, are lighted toindicate a vehicle forward or reverse, respectively, mode of operation.Indicia light 142 is steadily lighted to indicate a transmission neutralcondition and is flashed to indicate a preselected but not yet confirmedneutral condition. Indicia light 144 is lighted to indicate system 104is operating in the automatic preselection mode of operation.

If the control system (104)/method is allowed to remain in the automaticpreselect mode of operation for an extended period of time during whichvehicle speed (output shaft speed) is relatively constant and shifts arenot occurring, the vehicle operator may not be attentive to the displayconsole and an automatic shift into sustained neutral, resulting from anunnoticed, automatic initiated preselection of a gear change and anaturally occurring vehicle drive train torque reversal, may beunexpected and/or undesired which may be annoying and/or detrimental tothe vehicles performance.

To minimize and/or eliminate the occurrence of unintended/unexpectedshifts to sustained neutral when operating in the automatic preselectmode of operation of the previously proposed semi-automatic shiftimplementation control system, the enhanced mode control method/systemof the present invention is provided.

FIG. 4 illustrates the enhanced mode control system/method 200 of thepresent invention in flow chart format. If the system 104 is in theautomatic preselect mode of operation, the current vehicle (outputshaft) speed (OS) is sensed as well as the condition of the shiftactuator. The conditions of the shift actuator are defined as, (i) ifthe transmission is involved in a shifting operation, Shift=True and(ii) if the transmission is not involved in a shifting operation,Shift=False. If, for a predetermined period of time (REF), sixty secondsfor example, the vehicle exhibits stable operating conditions, i.e.,transmission not shifting and vehicle speed relatively constant, thenthe control system is automatically caused to operate in the manualpreselect mode of operation.

Accordingly, it may be seen that an enhanced control is provided for arelatively simple and inexpensive semi-automatic shift implementationcontrol system (104)/method for a mechanical transmission system 10having a manual and an automatic preselect mode of operation andrequiring only an ECU, a control console, a transmission shift actuator(112/70/96) and two speed inputs to be added to vehicle mechanicaltransmission system.

Although the present invention has been described with a certain degreeof particularity, it is understood that various changes to form anddetail may be made without departing from the spirit and the scope ofthe invention as hereinafter claimed.

I claim:
 1. A control method (200) for controlling a vehicularsemi-automatic mechanical change gear transmission system comprising afuel throttle controlled engine (E), a multi-speed change gearmechanical transmission (10), a manually controlled master frictionclutch (C) drivingly interposed between the engine and the transmission,a first sensor (98) for providing a first input signal indicative oftransmission input shaft (16) rotational speed, a second sensor (100)for providing a second input signal (OS) indicative of the rotationalspeed of the transmission output shaft (90) under at least certaintransmission operating conditions, a nonmanually controllabletransmission actuator (112, 70, 96) for controlling shifting of thetransmission and for provide a signal indicative of transmissionshifting (Shift=T) and not shifting (Shift=F) conditions thereof, a modeselector (108) for manual selection of either a manual or an automaticpreselection mode of operation and for providing a mode input signalindicative of said selected mode, and a central processing unit (106)for receiving said input signals and for processing same in accordancewith predetermined logic rules to issue command output signals, saidcentral processing unit including means responsive to manual andautomatic preselection of a transmission shift from a currently engagedratio for automatically issuing command output signals to said actuatorto cause the transmission to be shifted into neutral;said methodcharacterized by: if said central processing unit is operating in saidautomatic preselection mode of operation, sensing the rotational speedof said output shaft and the transmission shifting/nonshiftingcondition; and if, for a predetermined period of time (REF), the speedof said output shaft is substantially constant, and said transmission isnot shifting (Shift=F), then causing said control processing unit tooperate in the manual preselection mode.
 2. The method of claim 1wherein the speed of said output shaft is determined to be substantiallyconstant if, during the period of time, the speed does not vary by morethan ten percent (±10%) from the initial speed (OS_(o)) at the beginningof the period of time.
 3. A mode control (200) method for a controlsystem (104) for semi-automatic implementation of manually andautomatically selected shifts of a vehicular mechanical change geartransmission system comprising fuel throttle controlled engine (E), amulti-speed change gear mechanical transmission (10), a manuallycontrolled master friction clutch (C) drivingly interposed between theengine and the transmission, a first sensor (98) for providing a firstinput signal indicative of transmission input shaft (16) rotationalspeed, a second sensor (100) for providing a second input signalindicative of the rotational speed of the transmission output shaft (90)under at least transmission engaged in a known gear ratio conditions anda nonmanually controllable transmission actuator (112, 70, 96) forcontrolling shifting of the transmission, said control systemcharacterized by;means (120, 122, 124/132) for manually selecting anupshift or a downshift from a currently engaged transmission ratio orfrom neutral to a selected ratio and for manually selecting operation inan automatic preselect mode, and providing a third input signalindicative of said selection; indicia means (120, 122, 124) forindicating selection of the automatic preselect mode and for indicatingselection but not confirmed execution of a shift from the currentlyengaged transmission ratio; a central processing unit (106) forreceiving said first, second and third input signals and for processingsame in accordance with predetermined logic rules to issue commandoutput signals, said central processing unit including;(a) meansresponsive to manual selection of operation in an automatic preselectionmode (i) for issuing a command output signal to said indicia means toindicate that the automatic preselect mode has been selected, (ii) fordetermining the desirability of a shift from the currently engaged ratioand to select such a shift if desirable and (iii) for issuing commandoutput signals to said indicia means to provide an indication that anupshift or downshift, as appropriate, has been selected; (b) meansresponsive to selection of a transmission shift from a currently engagedratio for issuing command output signals to said actuator to bias thetransmission to be shifted into neutral; (c) means responsive to (i) aselection of a shift from a currently engaged ratio into a selectedratio and (ii) confirmation of a transmission neutral condition for (i)sensing manual substantial synchronization of the transmission and (ii)thereafter for issuing command output signals to said actuator to causethe transmission to be shifted into the selected ratio; and (d) meansfor confirming execution of a selected shift and for issuing commandoutput signals to said indicia means to terminate the indication of aselected shift; said mode control method characterized by: if saidcentral processing unit is operating in said automatic preselection modeof operation, sensing speed of said output shaft and the transmissionshifting/nonshifting condition; and if, for a predetermined period oftime (REF), the speed of said output shaft is substantially constant,and said transmission is not shifting (Shift=F), then automaticallycausing said central processing unit to operate in the manualpreselection mode regardless of previous manual selection of operationin said automatic preselection mode.
 4. The method of claim 3 whereinthe speed of said output shaft is determined to be substantiallyconstant if, during the period of time, the speed does not vary by morethan ten percent (±10%) from the initial speed (OS_(o)) at the beginningof the period of time.
 5. A control method for a vehicularsemi-automatic mechanical transmission system of the type having atleast two selectable modes of operation including a selectablesemi-automatic mode of operation wherein the transmission isautomatically shifted from an engaged ratio into neutral and is retainedin said neutral condition pending manual system manipulations by thevehicle operator, said method characterized by:if said system isoperating in said semi-automatic mode of operation, sensing therotational speed of the transmission output shaft and the transmissionshifting/nonshifting condition; and if, for a predetermined period oftime (REF), the speed of said output shaft is substantially constant,and said transmission is not shifting (Shift=F), then automaticallycausing said system to operate in a mode other than said semi-automaticmode.
 6. The method of claim 5 wherein the speed of said output shaft isdetermined to be substantially constant if, during the period of time,the speed does not vary by more than ten percent (±10%) from the initialspeed (OS_(o)) at the beginning of the period of time.
 7. A controlsystem for a vehicular semi-automatic mechanical transmission system ofthe type having at least two selectable modes of operation including aselectable semi-automatic mode of operation wherein the transmission isautomatically shifted from an engaged ratio into neutral and is retainedin said neutral condition pending manual system manipulations by thevehicle operator, said system characterized by:means effective if saidsystem is operating in said semi-automatic mode of operation, forsensing the rotational speed of the transmission output shaft and thetransmission shifting/nonshifting condition; and means effective todetermine if, for a predetermined period of time (REF), the speed ofsaid output shaft is substantially constant, and said transmission isnot shifting (Shift=F), then and for automatically causing said systemto operate in a mode other than said semi-automatic mode in response tosaid determination.
 8. The method of claim 7 wherein the speed of saidoutput shaft is determined to be substantially constant if, during theperiod of time, the speed does not vary by more than ten percent (±10%)from the initial speed (OS_(o)) at the beginning of the period of time.9. A control system for a vehicular semi-automatic mechanicaltransmission system of the type having at least two selectable modes ofoperation including a selectable semi-automatic mode of operationwherein the transmission is automatically shifted from an engaged ratiointo neutral and is retained in said neutral condition pending manualsystem manipulations by the vehicle operator, said system characterizedby:means effective if said system is operating in said semi-automaticmode of operation for sensing the transmission shifting/nonshiftingcondition; and if, for a predetermined period of time (REF), and saidtransmission is not shifting (Shift=F), then automatically causing saidsystem to operate in a mode other than said semi-automatic mode.
 10. Acontrol method (200) for controlling a vehicle semi-automatic mechanicalchange gear transmission system comprising a fuel throttle controlledengine (E), a multi-speed change gear mechanical transmission (10), amanually controlled master friction clutch (C) drivingly interposedbetween the engine and the transmission, a first sensor (98) forproviding a first input signal indicative of transmission input shaft(16) rotational speed, a second sensor (100) for providing a secondinput signal (OS) indicative of the rotational speed of the transmissionoutput shaft (90) under at least certain transmission operatingconditions, a nonmanually controllable transmission actuator (112, 70,96) for controlling shifting of the transmission and for provide asignal indicative of transmission shifting (Shift=T) and not shifting(Shift=F) conditions thereof, a mode selector (108) for manual selectionof either a manual or an automatic preselection mode of operation andfor providing a mode input signal indicative of said selected mode, anda central processing unit (106) for receiving said input signals and forprocessing same in accordance with predetermined logic rules to issuecommand output signals, said central processing unit including meansresponsive to manual and automatic preselection of a transmission shiftfrom a currently engaged ratio for automatically issuing command outputsignals to said actuator to bias the transmission to be shifted intoneutral;said method characterized by: if said central processing unit isoperating in said automatic preselection mode of operation, sensing thetransmission shifting/nonshifting condition; and if, for a predeterminedperiod of time (REF), said transmission is not shifting (Shift=F), thencausing said control processing unit to operate in the manualpreselection mode.